CSE 231
Fall 2009
Programming Project #4
Assignment Overview
This project focuses on string manipulation, as well as more experience with control. It is due
Monday, October 12th before midnight. That is two weeks, longer than normal, because of the
exam on October 8th. If you can, you should consider getting it done before the normal deadline.
Up to you.
The Problem
The 196-algorithm is a procedure for creating a palindromic integer: an integer that has the
same value when examined forwards or backwards. Examples of palindromic integers are: 88,
121, 2332, 12321, etc. The 196-algorithm is as follows.
1. If the integers is a palindrome, then print that integer
2. Otherwise, take the integer and its reversal and add them together.
3. With the sum, repeat the process starting at step 1.
Here are some examples:
56: 56+65=121! palindrome
57: 57+75=132; 132+231=363! palindrome
87: 87+78=165; 165+561=726; 726+627=1353; 1353+3531=4884! palindrome
89: 24 steps to the palindromic number 8813200023188
It is called the 196-algorithm because the integer 196 is the first number that, it appears, does not
converge to a palindromic number. Such a number is called a Lychrel number (see
http://en.wikipedia.org/wiki/Lychrel_number). Though it hasn’t been mathematically proven
that 196 doesn’t converge, it has been shown to not converge out to a number containing 300
million digits!
Program Specifications
You project will do the following:
1. Prompt for two integers. These two integers constitute the range of integers (inclusive) of
the integers that will be checked.
2. After the program runs, you will report the following statistics for the numbers examined
in the given range:
a. The number of “natural” palindromes (numbers in the range that are already
palindromes, such a 11, 121, 3553)
b. The number of non-Lychrel numbers (numbers which eventually yield a
palindrome using the 196 algorithm)
c. The number of Lychrel numbers encountered. Assume a maximum of 60
iterations to indicate a Lychrel number
d. Because Lychrel numbers are rare, report each Lychrel number as it occurs.
Deliverables
proj04.py -- your source code solution (remember to include your section, the date, project
number and comments).
1. Please be sure to use the specified file name, i.e. “proj04.py”
2. Save a copy of your file in your CS account disk space (H drive on CS computers).
3. Electronically submit a copy of the file.
Assignment Notes:
One of the main issues is converting values back and forth between integers and strings (using
the int() and str() functions). Determinations of palindrome and number reversal should be
done as strings, while clearly addition must be done with integers.
You are free to use any of the code we showed in class concerning palindromes. Remember that
there are no issues about capitalization or non-characters in this example since we are restricted
to dealing with sequences of integers.
Remember that python has no restriction on the size of an integer.
To clarify the problem specifications, we provide at the end of this document a snapshot of
interaction with the already written program.
Getting Started
1. Using IDLE create a new program.
2. If you are in a CSE lab, select the H: drive as the location to store your file
3. Save the name of the project: proj04.py
4. Create the preface print information and prompt for the user integers
5. Run the program and fix any errors
6. Use the web site to hand in the program (incomplete as this point but you should continually
hand things in)
7. Now, take the user number and check if it is a palindrome
8. Again, if you solve that save the program, as well as hand it in.
9. Now implement the reverse and add process. Combine this with the palindrome check.
10. Now see if you can do this iteratively for a range of numbers
11. Finally, check the counts at the end and print out the results.
12. Now you enter a cycle of edit-run to incrementally develop your program.
13. Hand in your final version.
Sample Interaction